schbidenhelm



F. W. SCHEIDENHELM.

CONSTRUCTION 0F DAMS.

APPLICATloN r|LED1uNE19.1915.

' Patented Sept. 16, 1919.

2 SHEETS-SHEET 1.

E11/141Mo@ FW. SCHEIDENHELM (QPS PLHNE OFFIIHLUBE F. W. SCHEIDENHELM. CONSTRUCTION 0F DAMS.

APPLICATION FILED IUNE I9. I9I5.

3mm/whoa, E W SCHEIIJEIIIHELNI FREDERICK W. SCHEIDENHELM, OF PITTSBURGH, PENNSYLVANIA.

CONSTRUCTION or DAMS.

Specification of Letters Patent.

Patented Sept .16, 1919.

Application led June 19, 1915. Serial No. 35,085.

To all whom it may concern:

Be it known that I, FREDERICK W. SCHEIDENHELM, a citizen of the United States, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented certain new and useful mprovements in the Construction of Dams, of which the following is a specification, reference being had to the accompanying drawings.

rihe present invention relates to new and useful improvements in the art of dam building and seeks generally to advance the practice of this art by providing a scheme or system whereby a dam may be irmly and securely anchored against horizontal movement or gliding on the foundation material whereon the dam is built. Except where indicated to the contrary, the word dam as used herein is intended to include dams, retaining walls and the like.

More particularly the invention aims to provide for the dam an anchoring means which is of such nature that the weight of the underlying material, upon which the dam is founded, is utilized as one of the Componentg which resist the horizontal movement or sliding of the dam.

More specifically, the present invention provides for the application of a dam body, of an anchoring wall or walls which are rigidly and iirmly tied thereto and are extended to a considerable depth into the material upon which the dam is founded, so that the plane of failure (which temi will be hereinafter de'inedl of the foundation material is lowered a considerable distance below the main footings of the dam.

Another and iin rtant object of the invention is te so design and relate the anchoring wall or walls to the dam body that the resistance to horizontal movementv or sliding, which the foundation material underlying' the dam body will then oder to the dam body, will be transmitted 'by a shearing or Cantaliver action to the dam body.

Still another object of the invention is to provide an anchoringV wall which, while lpossessed of the characteristics above vset forth, is further so designed that it will also seve as a cut-0E for preventing impounded liquid from reaching the footings or base of a dam, or the foundation material underlying the dam.

The above, and other incidentalobjects of a Similar nature, which will be hereinafter Vthroughl the hollow dam of Fi more specifically treated, are accomplished by such means as are illustrated in the accompanying drawings, described in the following specification, and then more particularly pointed out in the claims which are appended hereto and form part of this application.

With reference to the drawings, wherein there has been illustrated the preferred emhodiment of this invention, as it is reduced to practice, and throughout the several views of which similar reference numerals designate corresponding parts,

Figure l is a transverse vertical section taken through ya solid dam and showing the anchoring wall located'at the heel of the .dam (via, at the lower,upstream edge of the dam) Fig. 2 is a transverse vertical section taken through a hollow dam and illustrating the manner in which the anchoring wall may be -applied to the heel thereof;

Fig. 3 is a horizontal section taken g. 2, in a plane immediately above the footings of the dam and illustrating particularly the manner in which diagonally disposed tie rods are embedded in the anchoring wall and buttressesg Fig. e is a transverse vertical section taken through a hollow; .dani and illustrating an anchoring wall located at the heel of the dam body and a somewhat dierent form of anchoring wall located at the toe thereof (En, at the lower downstream edge thereo Fig. 5 is a transverse vertical section taken through a solid dam and showing a modified form of anchoring wall applied to the toe thereof; and

' Fig. 6 is a transversev vertical section wherein a modified form of anchoring wall is shown applied at the heel of a dam originally constructed without such an anchoring wall. v

ln taking up the description of the invention as illustrated in the vseveralviews of the accompanying drawings, referencev will irst 'be had particularly to Fig. 1, which, while it discloses one particular emlbodiment of the invention, also fully discloses the basic principle upon which the other embodiments `of the invention are founded. j

. ln this figure the dam, designated by the letter A., is shown as being of the solid type 'and having a vertical upstream face. Re-

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garding the particular design of the dani body A, it will, however, hereinafter become apparent that the body may be of design which is thought best to meet the conditions under which the dam is constructed;

for the eliiciency of the anchoring Wall, generally designated by the letter B, is not materially increased or decreased by variations in the design of the dam, it being merely necessary that corresponding changes in detail be made in the anchoring wall. The dam may be straight or curved or otherwise in plan.

The anchoring wall B is extended to .a considerable depth into the foundation material C upon which the dam is built and is so proportioned that it will be capable of withstanding the strains resulting in it in resisting the horizontal movement or sliding of the darn. Preferably, the anchoring'wall is located, as in Fig. l, at the heel of the dam. lf, however, the conditions obtaining maire it expedient to do so, the anchoring wall may be placed at an intermediate point between the heel and toe without departing in any way from the spirit of the present invention. In fact, as will be hereinafter more fully explained, and as illustrated in Fig. 5, it is in some instances desirable (and the present invention comprehends such possibility) to apply the anchoring wall to the toe of the dam, or to both heel and toe, as illustrated in Fig. el.

It is absolutely necessary and essential in the present invention that the anchoring wall B, whenit is applied at the heel of a dam, as in Fig. l, be rigidly and securely tied into the body of the dam, so that it may not be shea-red or broken off from the dam body as a result of the extreme stresses to which it is subject, especially when the height, and hence the pressure, of the impounded water is abnormal. rlhere has, therefore, been provided a plurality of horizontally disposed tie and reinforcing rods which extend through the body of the dam adjacent the base thereof and into that portion of the dam to which the anchoring wall is rigidly attached. There has also been provided a plurality of diagonally extencL'ng tie and reinforcing rods 11, the upper ends of which extend a considerable distance into the body member A. These rods l1 are preferably disposed at an angle of yapproximately forty-live degrees with the horizontal and traverse the angle D which would be dened by the intersection of the f downstream face 1Q of the anchoring wall and the base face 13 of rthe body member. As shown in Fig. l, the angle D is lled with concrete to strengthen the dam at the junction between the anchoring wall and the bddy member and to protect the rods 11.

lt will now be observed that, among other c5 functions, the rods 10 and/'1l adequately terasse serve to tie the anchoring wall into the body A and that they, therefore, rigidly and securely unite the anchoring wall and body. Thus, as will be hereinafter explained, the resistance which the material underlying the dam body offers to the horizontal movement of the anchoring wall is transmitted by a shearing or cantaliver action to the dam body. Hence, in turn, the underlying material offers resistance to the horizontal movement of the dam body itself. Forthis reason, the anchoring wall is provided with a plurality of vertically extending. metallic, further reinforcing members 14, which project at their lower ends to the approximate bottom of the anchoring wall and extend at their upper ends a considerable distance into the body These reinforcing members 14 are located immediately adjacent to the downstream face 12 of the anchoring wall for, as is well known, concrete is not capable of withstanding great tensile stress, and it is, therefore, necessary to reinforce a concrete body immediately adjacent to that face which is subject to tensile stress. Obviously, as will be seen upon reference to Fig. l, any resistance offered by the foundation material to the horizontal, downstream movement of the anchoring wall B will cause tensile stress in the concrete (and hence in the members 14 and 1l) near the downstream face 12. Therefore, through the medium of the thus reinforced anchoring wall B, the resistance' which the material underlying the dam of- 10o fers to the horizontal movement of the an.- choring wall is transmitted to the body A, by a shearing or cantaliver action.

lt is now desired, in concluding the description of the actual construction of the 105 invention, as embodied in Fig. l, to particularly emphasize the fact that the members 10, 11 and 14 serveto securely unite the anchoring wall B with the body A. and to tie it thereto, so that the member B will serve 11o as an effectual anchoring means, capable of withstanding all the stresses to which it will be subjected.

ln proceeding with the explanation of the results obtained from 'the incorporation in a 115 d-am,'0f such an anchoring wall as the member B, it is first to be explained that, generally speaking, a dam depends for safety, against horizontal movement or sliding, upon the roughness or frictional resistance of the foundation material.

ln the case of dams of the types at present in use, the total resistance to sliding is equal to the product of the multiplication of the weight of the dam and any vertical v Water load by the coefficient of friction (or roughness) between the baseof the-dam and the foundation material upon which the dam is built-plus, of course, such slight resistat the heel or other portion of the dam, if the dam have such cut-off walls. Such cutoff walls have, however, been of such a nature (owing to the' lack of proper reinforcing and tying elements), that, if subjected to considerable stresses, they will crack or part from the body of the dam, thus not merely failing to .prevent the sliding of the dam, but also thereafter being unable to perform their rimary function of preventing the impoun ed water from percolating under the base of the dam. 'Generally speal'iing, therefore, a dam fails through sliding 1f the horizontal pressure of the impounded water against the dam is suiiicient to lovercome a resisting force equal to the weight o f the dam and any vertical water load multiplied by the coefficient of friction between the base ofthe dam and the material upon which the dam is founded. Failures of dams have occurred in this manner, and in .some instances with disastrous results, suchl failures by horizontal movement or sliding usually having been occasioned when the foundation material upon which the dam was built was laminated or granular in` y founded, as does also the extent to which the surfaces of least resistance approximatestructure.

Heretofore the primary means of increasing resistance to horizontal movement or sliding of dams has been to increase the weight of the dam body. A secondary means has been to rou hen by notching, or toothing, the surface o? contact between the base of the dam and the underlying foundaltion material, for the purpose of increasing the coecient of frictional resistance. The former means is very costly. The latter means is effective only where the material upon which thedam is founded consists of a considerable depth of rock which is not laminated.

By the present invention, however, the resistancenecessary to prevent the horizontal movement or sliding of a dam is satisfactorily provided by means of an anchoring wall such as the member B inV Fig. 1. ln explanation of this statement, it is to be primarily observed that the plane of failure of the foundation material C is lowered to the very bottom of the anchoring wall B, instead of being located at the base of the main footings of the dam, as has been the case in prior constructions. By the term plane of failure, as used herein and on the drawings accompanying this application, is meant the surface, approximating a lane or planes extending through the founation material, along which the total resigtance to the horizontal movement of the dam is less than: it is along any other surfaces or approximate planes. It is found in practice that the plane of failure. may, and usually does, consist of a plurality of surfaces or approximate planes. Thus in Fig. 1 the plane of failure actually consists of two component planes. The one designated in Fig. 1 as lane of failure E begins at approximate y the bottom of the anchoring wall B and-extends in an approximately horizontal direction to a point, such as 15, which is in approximately vertical alinement with the down'stream'edge' or -toe of the dam body A. The other-designated in Fig. 1 as plane of failure Ea extends from a point such as 15 and inclines upward and downstream. This change in inclination of the entire plane of failure is due to the fact that upstream from' the approximately vertical plane P, which extends through the downstream edge of the dam body A and the point 15, the underlying foundation materiallis confined against upward movement by the downward pressure of the dam body A.

It has further been` found in practice that the .inclination of the plane of failure (especially as to the downstream portion thereof) and the point of beginning of the inclination of the downstream portion of plane of failure depend upon the nature of the material upon which the dam is dation material to be utilizedY as effectively v in 'resisting sliding as the weight of the dam body itself. The result is equivalent to making that portion of the foundation material which lies above the plane of failure act as a part of the dam itself, in so far as resistance to horizontal movement or sliding is concerned However, the presentinvention provides even additional resistance to horizontal movement or sliding of the dam. This is due -to the effect of the force of gravity in resisting the upward (and downstream) movement of the material in the approximate triangle F which is 'bounded by the plane of failure Ea, the approximately vertical plane P, and the surface of the foundation material indicated at S.

Accordingly, under the present' invention,

.the total resistance offered to the horizontal movement or sliding of the dam will consist of the following components:

1. The sum of the weights of the 'body of the dam, the anchoring wall B and any vertical water load, all multiplied by the coefficient of frictional resistance of the foundation material. V 2. The weight of the foundation material in the approximate rectangle G (bounded by the base of the dam, the downstream face 12 of the anchoring wall, the plane of failure E, and the approximately vertical plane P) multiplied by the coefficient of frictional resistance of the foundation ma- 'terial.

3. The weight of the material in the approximate triangle F multiplied by an expression taking into consideration both the effect of frictional resistance in the planes P and Ea and also the effect of the force of gravity on the material within the approximate triangle F.

It is evident from the foregoing that only the first of these three items is a material factor in dams as heretofore constructed, the second and third items being brought reliably into play solely as the result of the use of the anchoring wall B. 'These latter items may, and in an actual application did, amount to more than twice the rst item, hence the present invention will considerably lessen the cost of making a dam safe against failure by horizontal movement or sliding. Also, for equal weights of dam body (in the cases of dams of the same type), the present invention will allow the resistance against failure by horizontal movement or sliding to be greatly increased as compared with a dam which does not embody this invention. lt is particularly efficient when the foundation material consists of laminated. rock which has a low coefficient of friction, or of granular material such as clay, gravel, sand and the like.

It is further to be noted that while the primary function of the anchoring wall is as above described, y t it may at the same time be made to perform the function of a cut-olf wall, viz., to prevent the impounded water from percolating or passing under the base of the dam.4

From the foregoing description the essential features of the invention, the basic principle involved, and the manner in which the embodiment of this principle in a dam serves to greatly increase the resistance offered to horizontal movement or sliding will, it is thought, now be appreciated, and the description of the various modifications or different embodiments of the invention will now'be taken up.

ln the embodiment illustrated in Figs. 2 and 3, the anchoring Wall, which is therein designated by the numeral 17, may be applied to a dam of hollow construction. As

shown, the anchoring wall is extended downwardly from the heel of the dam to a considerable depth into the foundation material upon which the dam is built. Vertical reinforcing rods or equivalent elements, indicated at 18, are embedded in the anchoring wall, adjacent to the front and rear face thereof.

These reinforcing elements 13 are located according to the stresses in the member 17 and are extended upwardly into the upstream dec-lr or wall 20 of the dam so that the resistance odered by the anchoring wall 17 will be transmitted into the dam by a shearing or cantaliver action, as in the embodiment in Fig. 1. A plurality of longitudinal reinforcing members indicated at 19 is also embedded in the anchoring wall adjacent to both the upstream and downstream faces thereof. As shown in Fig. 3, the upstream wall 2O of the dam is supported by transversely spaced, vertical buttresses 21 which are strengthened at their junction with the upstream wall, as at 22., and especially at their junctions with theanchoring wall. The depending reinforcements of concrete 23 serve to strengthen the junctions of the anchoring wall 17, the upstream wall 20, and the buttresses 21 and to protect the embedded tie and reinforcing elements 25. Horizontal tying and reinforcing rods indicated at 24, equivalent in function to the members 10 in Fig. 1,A pass through the uper portion of the anchoring wall 17 and into the buttresses. The substantially U- shaped tie and reinforcing rods indicated at 25 are also applied. yhese rods are disposed with their arm portions extending longitudinally through the buttresses and upwardly in a downstream direction. The bight portions of these tie rods 25, indicated at 26, pass through the reinforcements 23, and through the anchoring wall 17 as in Fig. 3.

The functions of those vertical reinforcing members 18 which are adjacent to the downstream face of the member 17, the horizontal rods 24 and the inclined rods 25 are similar to the functions ofthe members 14, 10 and 11, respectively, of Fig. 1, and need not, therefore, be recited in detail. lt is important, however, to direct particular attention to the fact that the anchoring wall, when 110 embodied in a dam of hollow construction, is united with the body of the dam in essentially the same manner as when the anchoring wall is applied to a dam of solid construction. '.llhe sum of forces resisting the 115 horizontal movement or sliding of the dam illustrated in Figs. 2 and 3 is equivalent to the sum of forces above described as resisting the horizontal movement or sliding of the dam of Fig. l.

lt is to be noted that under certain conditions, especially in cases where the foundation material is not required to furnish any considerable resistance to the horizontal movement or sliding of the dam, it is feasi- 125 ble to omit the inclined rods 11, shown in Fig. 1, or the inclined rods 25, shown in Fig. 2, together with the reinforcing shown in the angle D of Fig. '1 and below the main footings of the body 21 at 23 in Fig. 2.

Reference will now be had to Fig. 4, wherein a further modification of the application of thev present invention is shown. In`Fig. 4 the dam is of thewell-known hollow type, as in Figs. 2 and 3, and is similarly provided with an anchoring wall 27 located at the heel of the dam. This anchoring wall 27 and the means by which it is united with the dam body, are equivalent to the corresponding features above explained in connection with Figs. 2 and 3 and need not, therefore, be further described. However, in addition to the heel anchoring wall 27, there is provided in Fig. 4, a second anchoring wall, designatedgenerally bythe letter H. This anchoring wall is located, as shown, at thetgeofthe dam andv is substantially L-shaped in cross section. Approximately vertical reinforcing' members, indicated at '28, pass through the vertical portion 29 of the member H and are located preferably adjacent to the downstream face of the portion 29, for the reasons explained in connection with the reinforcing members 14 of Fig. 1. The advantage in making the toe anchoring wall H substantially L-sha ed will be apparent when it is considered t at the vertical and horizontal portions of the member H act in the same manner as do the arms of a bell crank lever. The resistance which the foundation material offers to the horizontal'movement of the vertical portion 29 of the member H would normally tend, were it not for the horizontal portion 30, to turn the member 29 relatively upwardly in an upstream direction. Such turning, however, is counter-balanced by the resistance which the foundation material offers Ato thedownward movement of the horizontal portion 30. It is to be noted that diagonally extending reinforcing rods 31, or equlvalent elements, are embedded in the member H, extending adjacent to the lowerface of the horizontal portion 30, so as to reinforce the portion 30 against the tensile stresses caused in that member b the resistance of the foundation materia to the downward movement of the member 30.

The horizontal portion 30 of the anchor-4 ing wall H furthermore in effect becomes a part of the base or footings ofthe dam, thus serving to increase the area of the foundation material over which the load of the dam is distributed, and hence caus the unit pressures on the foundation materia to be less than if such horizontal portion 30 were omitted.

It is now desired to direct articular attention to the fact that the pcro able location of that component of the lane of failure of the foundation materia which is indi-- cated at 32, is further downstream than in: the case where the dam is constructed with only the heel anchoring wall. Obviously the inclined plane of failure or component 32 will intersect the approximately horizontal component 33 (which comprehends the bottom of the heel and toe anchoring walls) at a point such as 34 which is in approximately vertical alinement with the downstream edge ofthe horizontal portion 30 of the anchoring wall H;for the underlying foundation material upstream from the approximately vertical plane 35 (which extends through the downstream edge of the member 30 and the point 34) is confined in the same manner as is the material within the approximate rectangle G in Fig. 1.

From the description thus far given, it will now be apparent that when the dam is constructed as in Fig. 4, with both heel and toe anchoring walls, the resistance to horizontal movement or sliding of the dam is materially increased over even the resistance' offered by the construction of .Fig. 1. VThe resistance to sliding of a dam constructed as in Fig. 4, consists of the sum of the following components 1. The sum of the weights of the dam, the heel and toe anchoring walls, and the vertical water load, all multiplied by the coefficient of frictional resistance of the foundation material.

2. The sum of the weights of the foundation material in the approximate rectangle K and the approximate rectangle L multiplied by the coeflicient of frictional resistance of the foundation material.

3. The weight of the material in the approximate triangle M multiplied by an expression taking into consideration both the effect of the frictional resistance in the planes 32 and35 and also the effect of the force of gravity on the material within the 'of Fig. 4 may be used alone, whenever desired, without in any way departing from the spirit of the invention, the advisability of such construction depending entirely upon the conditions obtaining at the dam site in question. l It is to be further explained that it is desirable to employ both the heel and toe anchoring mem ers when the materials upon which the dam is founded are soft or liable to crush, that is, when they are of low bearing value. If only the heel member were applied, the pressure of this member downstream against the foundation material underlying the footings of the dam lmight be such as to crush the material, thus weakening the dam foundation. By providing the toe member connection with the heel mem- .stream direction.

ber, however, that resistance to horizontal movement or sliding of the dam which would otherwise be distributed over the downstream face of the heel member only, may thus be distributed over the downstream faces of both heel and toe members, so that the foundation material will not be crushed l faces of the plane of failure would vary I correspondingly.

Under some conditions it may be' desirn able to eliminate the horizontal portion of the anchoring wall when the latter is placed at the toe of the dam. ln such cases the anchoring wall may, if desired, be provided with an approximately vertical downstream face, as illustrated in Fig. 5. This type olanchoring wall, indicated at 36 in Fig. 5, is applied to the toe portion of a dam body A and is secured thereto by the lm-shaped tying and reinforcing rods 37. In Fig. 5 such an anchoring wall is shown applied to a con crete dam of the solid type, but the use of such an anchoring wall is by no means con- "iined to dams of that type or of that material. 'lhe upper portions of these rods are extended into the body A of the dam, bending into horizontal position as shown, while the lower portions extend vertically through the anchoring wall adjacent to the downstream face thereof. lt will. be seen that the reinforcingmembers'? in reality perform. the same function which has hereinabove been attributed to the horizontal ortion 3G oi"- the l.-shaped anchoring wall i. of Fig. fl,

since they serve to prevent the anchoring` wall 86 Jfrom yielding in a relatively uplt will also be noted that the vertical portions of the rods 37 reinforce the anchoring wall 36 at the proper portion thereof, and that they aid in transmitting 'to the body or the dam, by a shearing or canta liver action, the resistance which is offered to the horizontal, downstream movement of the wall 86.

ln Fig. 6, a further modilcation of anchoring wall for the heel'oi a solid dam is illustrated. ln this form of the invention, the anchoring wall indicated at 39 is built up on the upstream side of the dam body ed which was originally constructed without such an anchoring wall. The wall 39 s united to the body 40 by the horizontal tie rods 4l, which pass through the upper pore tion of the anchorin wall and are suitably embedded in the body 4:0. Approximatel vertical reinforcing rods 42 pass throng neiaaea tleanchoring wall 39 adjacent to the downstream faoe thereof.

ln tying the anchoring wall to the body 40 and in bracing it in a manner adequate to withstand the strain, there are employed a lurality of tie rods 43. These rods are emedded at their upstream ends in the anchor ing wall 39 and extended beneath the base of the body l0 to suitably engage at their downstream ends in the toe wall a5. rlhe members 43 are preferably applied to the dam by digging or blasting tunnels beneath the base thereof to receive the members 43. rlhese tunnels are, of course, subsequently hlled with concrete or grout. The terminals of the rods 43 may be hooked or otherwise bent at either end, as indicated at 44 in Fig. 6.

lt will be readily appreciated that the form of anchoring wall shown in Fig. 6 is united with the body 4 0 of the dam in an unusually strong manner and that it will be capable of withstanding any stresses put upon it.- The anchoring wall 39 of Fig. 6 will act in the same manner as does the anchoring wall B of Fig. 1 to resist the sliding of the dam. That is, in the embodiment shown in Fig. 6, the resistance ol'ered by the foundation material to the horizontal, downstream movement of the anchoring wall 39 is transmitted successivel into the tie rods 43, the toe wall e5, an finally into the dam body 40.

ln reduction to practice, it has been found that the forms of the invention illustrated in the drawings, and referred to in the above description as the preferred embodiments of this invention, are the most efcient and practical; yet realizing that the conditions concurrent with the adoption or this device will necessarily vary, it is desirable to emphasize the fact that various minor changes in the details ci construction, proportion and arrangement or parts may be resorted to, when required, without sacrificing any of the advantages of this invention, as deiined by the appended claims.

For instance, the anchoring wall or equiv alent may be either continuous or discontinuous lengthwise of a dam. Likewise, the connection to the body or a dam need not necessarily be at the upper portion of an anchoring wall or equivalent, but instead the .necessary connection be made at the middle or lower portions or at more than 'one portion thereof.

l. A. dam including in combination a body portion, an anchoring wall extending lengthwise of said dam and downwardly into the foundation material' to a comparatively great depth, and means for transmitting horizontal thrustcfrom said body portion into the foundation material oversubstar1 lill ldd

llli

Leieea tially the entire downstream face of said anchoring wall, whereby the weight and frictional resistance of the foundation material lying in a downstream direction from said wall are utilized by said anchoring wall and means to resist sliding of the dam. f

2. In a gravity dam, the combination of a. body portion having a broad base, a mas sive projection on said base extending lengthwise thereof and downwardly into the foundation material to a comparatively great depth whereby any tendency of the dam to slide will be overcome by the resistance due to the weight of the earth lying in a downstream direction from said projection, and means for securely tying said projection to said base.

3. In a gravity type of concrete dam, the combination of a body portion having a broad base, massive projections on said base, the said projections being' extended lengthwise of said dam and downwardly into the foundation material to comparatively great depths, whereby the possible plane of 4failure by sliding of said dam is lowered to approximately the bottom of said projections, and reinforcing means extending from said base into said projections.

4. In a hollow gravity dam having a broad base, the combination with said base of a projection, the said projection extending lengthwise of said base and downwardly to a substantial distance into the foundation material, whereby the weight and frictional resistance of such material lying downstream from said projection are utilized to resist sliding of the dam and the possible plane of failure by sliding is lowered from the/'ibase of the body to approximately the bottom of said projection, and means for strengthening said projection to prevent the same from rupturing from said baseu 5. In a hollow gravity dam, the combination of a body portion having a broad base, a projection extending lengthwise thereof and downwardly into the foundation material to a comparatively great depth, whereby any tendency of the dam to slide will be resisted by the passive pressure against substantially the entire downstream face of the said projection, due to the weight and frictional resistance of the foundation-material lying in a downstream direction from said projection, and means for tying said projection to the said base.

6. In a hollow gravity concrete dam, the combination of a body portion having a broad base, projections on said base, the said projections being extended downwardly into the foundation material to comparatively great depths, whereby the weight of the foundation material lying between and downstream from said projections is utilized in lowering the possible plane of failure by sliding from the base of said dam to approximately the lower ends of said projections, and means for strengthening said projections to prevent the same from rupturing from the said base.

In testimony whereof I hereunto aiiix my signature in the presence of two witnesses.

FREDERICK vW. SCHEIDE NHELM.

Witnesses:

WILLIAM L. PAINE, H. A. DUNN. 

